Story

The story begins in the Land of Departure, where a trio of friends and Keyblade wielders—Terra, Aqua, and Ventus (Ven for short)—train under the Keyblade Master Eraqus to become Keyblade Masters themselves. Terra and Aqua take an exam to achieve the Mark of Mastery, but while Aqua passes, Terra fails due to the abundant darkness in his heart. Shortly after the test, another Keyblade Master, Xehanort, disappears, and a horde of mysterious creatures called the Unversed begin to appear throughout the worlds. Eraqus sends Terra to destroy the Unversed and find Xehanort. Ven is goaded into following Terra by Vanitas, Xehanort’s enigmatic apprentice, against Eraqus’s wishes. To watch over Terra and bring Ven back to the Land of Departure, Aqua is sent out to track her friends down.

Upon arriving in several worlds, Terra, Aqua, and Ven encounter various Disney characters, fighting off many Unversed along the way. Among the characters they meet is Mickey Mouse, the apprentice of the sorcerer Yen Sid, who is also on a mission to destroy the Unversed. Terra ends up attracting the attention of several Disney villains, who offer him the whereabouts of Xehanort in exchange for assistance in their own dark agendas. Terra reasons that Xehanort is after the seven Princesses of Heart—maidens who lack darkness in their hearts—and encourages Aqua to help them strengthen the light in their hearts, hoping it will draw Xehanort out. Aqua and Ven grow increasingly concerned for Terra when they hear rumors of him committing sinister deeds throughout other worlds. The three briefly reunite at Radiant Garden, where Aqua meets Kairi, a young girl containing a strong and pure light in the heart of her royal blood, and helps strengthen her light. Aqua and Ven also confront Terra, who distances himself from them to keep them out of the way of his increasingly dangerous dark powers. Terra and Aqua try to convince Ven to return to the Land of Departure, but he refuses until he is certain Terra will not fall into darkness.

Terra and Aqua eventually find themselves at Destiny Islands where they encounter Sora and Riku. Terra sees potential within Riku and deems him worthy of one day wielding the Keyblade, while Aqua senses strong ties with Sora and Riku to Ven and Terra, respectively and asks Sora to protect Riku from Darkness. Ven, meanwhile, comes across Xehanort, who reveals his intentions to use Ven’s heart to create a final Keyblade known as the Χ-Blade which he also says Master Eraqus had known all along. Ven returns to the Land of Departure to confront Eraqus, who tries to erase Ven to prevent Xehanort’s plans from succeeding. However, Terra, who had been sent there by Xehanort, attacks Eraqus and teleports Ven to safety to protect him. Upon his defeat, Eraqus is vanquished by Xehanort, who tells Terra to go to the Keyblade Graveyard and leaves the Land of Departure to be consumed by darkness. At Destiny Islands, Ven once again encounters Vanitas and learns of his past: Ven was once Xehanort’s apprentice, but due to his reluctance to use his inner darkness in battle, his heart was deemed too weak for Xehanort to use him as he intended, so he extracted the darkness in Ven’s heart and used it to create Vanitas, and then sent Ventus to be trained by Eraqus so that he may gain strength. As with Terra before him, Ven is instructed by Vanitas to go to the Keyblade Graveyard. Aqua, in the meantime, learns of Eraqus’s defeat from Yen Sid, who tells her to go to the Keyblade Graveyard as well.

Terra, Aqua, and Ventus gather at the Keyblade Graveyard, where the remains of the mysterious Keyblade War are found. Xehanort appears with Vanitas and reveals his plan to use the Χ-Blade to unlock Kingdom Hearts and unleash the forbidden secrets of the Keyblade War onto the various worlds, as well as to use Terra’s body as a new vessel for his own heart so that he may survive long enough to see his plans progress. In the following battle, the enraged Terra unleashes the darkness in his heart and is possessed by Xehanort, but his strong will remains within his discarded suit of armor, which comes to life as the Lingering Sentiment and defeats Xehanort, knocking him unconscious. Meanwhile, Ventus is forced to fuse with Vanitas to create the Χ-Blade, and their fusion, with Vanitas in control of Ven’s body, battles Aqua alongside Mickey, while the real Ven fights Vanitas from within his subconscious. Aqua shatters the Χ-Blade as Ven destroys Vanitas within his mind, but as a result, his heart became lost in the process. The destroyed Χ-Blade unleashes a massive explosion of light, which consumes everyone present and scatters them to the corridors of space.

Mickey saves Aqua and Ventus and brings them to Yen Sid’s tower, where Aqua learns that Ven has lost his heart and will not be revived until his heart returns. Aqua brings Ven’s catatonic body back to the ruins of the Land of Departure, where she unlocks the Chamber of Waking and creates Castle Oblivion from the ruins using Master Eraqus’s Keyblade. After leaving Ven to sleep within the chamber, Aqua goes to Radiant Garden to track down Terra-Xehanort, where she encounters and defeats him, who has lost his memories but still possesses Terra’s body. Terra then gains temporary control over his body and attempts to stop Xehanort from within by sending himself into the Realm of Darkness, but Aqua dives into the darkness and saves Terra from disappearing with her armor and Keyblade. She ends up getting trapped in the Realm of Darkness, unable to access her Keyblade, and begins a journey to return to her friends, albeit to no avail. Terra-Xehanort is discovered and taken in by Ansem the Wise, ruler of Radiant Garden, as his apprentice. Ven’s heart of light then finds its way to a young Sora is able to merge with his heart.

After the events of Kingdom Hearts II and Kingdom Hearts coded, Aqua comes across Ansem in the Realm of Darkness, with only a few of his memories remaining. He tells Aqua all about his encounters with Sora, and that Sora is now the only one who can stop the worlds from being engulfed in darkness and save all of those connected to his heart, including Ansem and Aqua themselves, Terra, and Ventus. Sora, having now read the letter from King Mickey, tells Kairi that he must undertake another quest in order to save everyone who is connected to him.